Type of question
Task oriented designed to lead to new ITU-T Recommendation(s).
Various mechanisms like RSVP or MPLS are being introduced into IP
networks to support voice over IP and other applications. The motivation,
for example, for VoIP over MPLS is to take advantage of these new network
capabilities, in those IP domains in the network where they are available,
in order to improve voice over IP service by:
- using label-switched-paths as a bearer capability for VoIP thereby
providing more predictable, and even constrained QoS,
- providing a more efficient transport mechanism for VoIP possibly using
header compression or suppression,
- using other advantages of MPLS, e.g. Layer 2 independence, integration
with IP routing and addressing, etc.
The advantages of such mechanisms for the delivery of satisfactory
end-to-end speech transmission performance can be understood in a
single-domain environment with one specific mechanism deployed.
Today quite unpredictable, however, is the level of speech transmission
performance through a concatenation of multiple IP domains which
individually deploy different mechanisms.
The deployment of multiple VoIP islands interworking via the conventional
PSTN will be a natural consequence of switch deployment practice:
- A network or service provider might wish to deploy VoIP as a PSTN
replacement to deliver PSTN-type voiceband services such as speech,
facsimile and voiceband data.
- A network or service provider might wish to deploy VoIP as a new type
of voice service.
- This will lead to multiple VoIP islands within a single carriers'
network as well as islands which arise due to calls which are routed
through multiple operators.
- If deployment is driven by growth and obsolescence then the transition
to a full VoIP solution will take 15 to 20 years, during which time
multiple islands will be the normal situation.
- Solutions which lead to retrofit requirements in order to solve QoS
problems, are very unlikely to be cost effective.
It is possible to avoid excessive numbers of islands by deploying
equipment and planning routing intelligently. Therefore, to enable operation
with such network configurations it will be necessary provide appropriate
Text of the question
a) that IP telephony connections may employ a multitude of IP domains;
b) that various signalling, routing and prioritization schemes can be
deployed in each of such IP domains;
c) that end-to-end speech transmission performance of connections
comprising of multiple IP domains will strongly depend on the interworking
of signalling, routing and prioritization schemes between different IP
d) that the deployment of VoIP equipment may be driven by growth and
e) that the transition to a full VoIP solution may take 15 to 20 years,
during which time multiple VoIP islands in the PSTN will be the normal
the following question should be studied:
- What are the conditions of interworking between multiple IP domains
that need to be satisfied in order to deliver satisfactory end-to-end
speech transmission performance and performance of other voiceband
a) The effects of interworking between multiple IP domains on VoIP
speech transmission performance;
b) The effects of interworking between multiple IP domains on the
transmission performance of voiceband services;
c) Deployment strategy: how to avoid excessive numbers of VoIP islands by
deploying equipment and planning routing intelligently.
Objectives and schedule
It is anticipated that the study will result in new ITU-T
The estimated time frame is less than one Study Period.
Relationship with other activities
- With other ITU-T Study Groups: SGs 2, 9, 11, 13, 16 (and maybe 4 and 15), SSG
- With other Bodies: ETSI EP TIPHON, ETSI TC STQ, TIA TR-41, IETF